The invention relates to scraper blades.
In another aspect the invention relates to a scraper blade useful as a wipe stick for cleaning the extrusion face of a spinneret.
Synthetic fibers are generally produced by melt spinning thermoplastic polymers. The thermoplastic polymers are heated to their melting point and then extruded through a plate having a plurality of orifices therein, usually referred to in the art as a spinneret. The filaments are formed as the melted polymer is forced or extruded through the orifices in the spinneret, cooled to a temperature below their melting point and then wound up to form a package of melt spun yarn. This freshly spun yarn is usually drawn to substantially improve its tenacity and textured or bulked by various processes known in the art. It is of course fundamental that the quality of the textured yarn can be no better than the quality of the yarn produced in the melt spinning operation.
One of the problems that frequently occurs during the melt spinning operation is the buildup of melted polymer on the outside face of the spinneret, usually adjacent the orifices. This polymer buildup, if not removed periodically, decomposes and turns very dark in color, and is pulled off in small pieces by the moving melt spun filaments exiting the face of the spinneret. The degraded polymer on the face of the spinneret can also distort the filament cross section which results in a nonuniform yarn or a yarn with a high Uster value. Further some of the degraded polymer pulled from the face of the spinneret ends up as dark specks in the yarn which also results in a nonuniform yarn.
In order to preclude the problems associated with polymer buildup on the face of the spinneret, the spinneret face is periodically wiped with a scraper or a wipe stick to remove any accumulation of polymer therefrom. As known in the art these scrapers or wipe sticks are generally made from a soft metal, such as brass. Although the spinnerets are made from materials generally much harder than brass, such as stainless steel, the brass wipe sticks still damage the outlet region of the spinneret orifices. In the event the brass wipe stick is nicked so as to cause a burr on the wiping edge, it can cause severe damage to the orifices of the spinneret because of the substantial difference in the temperature of the wipe stick as compared to the spinneret. In addition the brass wipe sticks require frequent resharpening of the wiping edge in order for the wiping operation to be effective.
An object of the invention is a scraper blade or a wipe stick that substantially lessens the possibility of damaging the spinneret during the wiping operation.
Another object of the invention is a scraper blade or a wipe stick that does not need to be resharpened nearly as often as a brass scraper or wipe stick.
Another object of the invention is a scraper blade or wipe stick that resists the tendency of the extruded polymer to stick thereto.